But more sophistication - combined with the global allure of the Internet that allows anyone, anywhere to buy and sell coins and ingots with the click of a mouse - has allowed scams to proliferate and forced the fight against fraud to use advancing technology.

Experts now are able to identify atomic components that can trace metals to their mining district of origin, providing a sort of DNA fingerprint. Combined with an unprecedented historical record recovered from the ocean floor, the process is generating excitement among numismatists - coin collectors - and hobbyists, who say it could help expose disguised worthless trinkets and validate the authenticity of others.

''There have been some exceptionally rare pieces questioned for a long time,'' said Beth Deisher, editor of Coin World magazine. ''If there is a process by which we can determine without question the origin of the gold, it could be a definite statement as to whether the pieces are real or fake.''

For Fred Holabird and David Fitch of Reno, the endeavor is a melding of decades in the mining industry, a love of history and a determination to bore out truth.

''It's sort of like detective work,'' said Fitch, who worked in mining exploration for more than 30 years and now consults. ''In forming an ore deposit, nature carries its own fingerprint of an area. No two sites are the same.''

''It's treasure hunting at its best,'' Holabird added.

Holabird, who worked in gold production, Fitch and Bob Evans, a geologist and coin curator in Hopewell, Ohio, first presented their research in 2003 and received an award last year from the American Numismatic Association. They presented an update to the American Academy of Forensic Science last year.

Numismatists have been following developments with interest, and agree the new technique could help stamp out fraud.

''It would constitute a major breakthrough,'' Deisher said. ''Over the centuries, we've learned that counterfeiters adapt to the situation. They are especially adept at using new technologies.''

Emerging science, she added, ''should slow them down significantly in our marketplace.''

Ironically, a shipwreck nearly 150 years ago has bolstered the modern mission.

The SS Central America was a side-wheel steamer that sank during an Atlantic hurricane in 1857. Many of its passengers had been miners returning from California, and the ship was laden with gold - hundreds of ingots and thousands of coins.

''This stuff is worth millions and millions of dollars,'' Fitch said.

One bar, dubbed ''Eureka,'' sold for $8 million.

Evans was the lead scientist for the 1989 salvage operation by the Columbus-America Discovery Group, and cataloged the rewards. Holabird - retained as an expert when insurers and the salvage company went to court to divvy up the treasure - inventoried the cache.

Besides fascination and awe, the riches raised from the sea floor provided a preserved record of the refining and marking techniques used by different assayers of the era.

''That gave the whole subject a real baseline,'' Evans said. ''Now we had 532 absolutely genuine ingots - no questions of their historical genuineness.''

Holabird, also a dealer of artifacts, said the treasures from the shipwreck magnified the problem. Some were high profile, like two ingots at the Smithsonian Institution from the collection of the late pharmaceutical executive Josiah Lilly.

''Mr. Lilly was an enthusiast,'' Evans explained. ''He probably believed they were real and there was no evidence to the contrary.

''The suspicions were heightened when the SS Central America came out and the real ingots made by a certain manufacturer didn't look at all like the ingots in the Lilly Collection,'' he said.

Holabird said it became apparent people were being duped.

''You realize they're selling for hundreds of thousands of dollars and some of them might not be real,'' he said. ''How do you tell the difference?

''It became more important to come up with a method to separate real from fake using science,'' Holabird said.

They turned to John Watling, an Australian chemist and pioneer of forensic fingerprinting of gold and diamonds.

Watling uses a machine called a Laser Ablation Inductively Coupled Plasma Mass Spectrometer to break samples down to the atomic level.

Using a tiny laser beam, a microscopic incision barely visible to the naked eye is drilled in a sample, and the resulting vapor is analyzed. The painstaking process allows scientists to detect trace and subtrace elements in the range of parts per billion.

Holabird and his team then use the data retrieved by Watling to develop a three-dimensional color display, or visual fingerprint, of the sample, making it easier to interpret.

''The differences show up very, very quickly,'' Holabird said.